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Biology > Exchange Surfaces and Breathing > Flashcards

Exchange Surfaces and Breathing Flashcards

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1
Q

Why are exchange surfaces needed?

A
  • Large multicellular organisms have a small surface area to volume ratio
  • Cells in the centre of the organisms would not receive any materials if multicellular organisms survived on diffusion alone
  • Multicellular organisms have a high metabolic rate so there is a need to exchange lots of materials quickly.
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2
Q

What is the rule for SA:V ratio?

A

The largest the SA:V of an organisms, the easier the exchange of substances by diffusion is.

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3
Q

What are the SA:V calculations for a cuboid?

A
  • Volume=Length x Width x Height

- Surface Area=(4xlengthxheight)+(2xheightxwidth)

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4
Q

What are the SA:V calculations for a cylinder?

A
  • Volume= 3.14xradius^2 x height

- Surface Area= (2x3.14xheight) + 2x3.14 x radius^2

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5
Q

What are the SA:V calculations for a sphere?

A
  • Volume= 4/3 x 3.14x radius^3

- Surface Area= 4 x 3.14 x radius ^2

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6
Q

What are the features of an efficient gas exchange system?

A
  • Large surface area
  • Thin layers
  • Rich blood supply
  • Ventilation (maintains diffusion gradient which makes process more efficient and faster_
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7
Q

What is the pleural cavity?

A
  • Space between the double membrane (pleural) enclosing the lungs
  • It is filled with a small amount of pleural fluid
  • This fluid lubricates the lungs
  • It also adheres the outer wall of the lungs to the thoracic cavity by water cohesion, so that the lungs expand with the chest while breathing
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8
Q

What are the functions of the nasal cavity?

A
  • Large surface area and good blood supply allows the air to be warmed as it passes into the body
  • Hairy lining which traps dust and bacteria in mucus and prevent them from reaching the lungs (this is not cillia)
  • Moist surfaces increases the humidity of the incoming air which reduces the evaporation of water in the lungs
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9
Q

What are the features of the trachea?

A
  • Pipe is supported by a layer of cartilage that holds the trachea open and prevents it from collapsing
  • Cartilage rings are incomplete to allow it to bend when food is swallowed down the oesophagus
  • Lined with ciliate epithelial and goblet cells that prevent dust and bacteria from entering the lungs
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10
Q

What is the bronchus?

A
  • The bronchus are extensions of the trachea that split into two for the left and right lung
  • This has a very similar structure to the trachea but smaller
  • Cartilage rings hold the pipe open
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11
Q

Why do ciliated epithelial cells contain many mitochondria?

A

To provide lots of energy for the cillian to waft

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12
Q

What are the bronchioles?

A
  • Bronchus splits into much smaller bronchioles
  • They are around 1mm or less in diameter
  • Have no cartilage and are held open by smooth muscle
  • When this muscle contracts, the bronchioles contract, which is dependent of air flow
  • They are lined with a thin layer of epithelial tissues making some gas exchange possible
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13
Q

What are alveoli?

A
  • Little air sacs where most of the gas exchange occurs
  • Each alveoli is about 200-300um in diameter
  • Made up of a thin layer of flattened epithelial cells as well as some collagen and elastic fibres
  • Elastic fibres causes recoil which helps move air out of the alveoli.
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14
Q

What are the features of efficient gas exchange system?

A
  • Large surface area (alveoli cover a surface area of around 50-75m^2)
  • Thin layers (short diffusion pathway, increasing speed of exchange)
  • Good, constant blood supply (maintains diffusion gradient by ensuring exchanged substances are moving to the area needed)
  • Ventilation (maintains diffusion gradient which makes process faster and more efficient)
  • Moist (maintain blood gas barrier to prevent gas from entering blood)
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15
Q

Why are gas exchange systems moist?

A

To aid diffusion by oxygen dissolving into the water. However ventilation causes this water to readily evaporate. The gas exchange system is helpfully adapted to efficiently gas exchange without losing too much water.

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16
Q

What is lung surfactant?

A

A phospholipid that coats the surfaces of the lungs. Without it, the watery lining of the alveoli would create surface tensions and cause the alveoli to collapse.

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17
Q

What brings about ventillation?

A
  • Pressure changes in the thoracic cavity

- Rib cage provides a cage in which pressure can be changes to facilitate breathing.

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18
Q

What happens in expiration?

A
  • Diaphragm moves up
  • Intercostal muscles move the ribs down and in
  • Thoracic volume decreases
  • Thoracic pressure increases
  • Air flows out of the lungs (to equalise the pressure difference)
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19
Q

What kind of process is expiration?

A

A largely passive process

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20
Q

What happens during inspiration?

A
  • Diaphragm moves down
  • Intercostal muscles move the ribs up and out
  • Thoracic volume increases
  • Thoracic pressure decreases
  • Air flows into the lungs (to equalise the pressure difference)
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21
Q

What kind of process is inspiration?

A

An active process

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22
Q

What is the composition of inhaled air?

A
  • 78% Nitrogen
  • 21% Oxygen
  • 0.04% Carbon Dioxide
  • <1% Water Vapour
  • <1% Other
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23
Q

What is the composition of exhaled air?

A
  • 78% Nitrogen
  • 15% Oxygen
  • 4% Carbon Dioxide
  • 3% Water Vapour
  • <1% Other
24
Q

How does a spirometer work?

A
  • Static lower half of tank is full of water
  • Mobile upper half of tank is full of oxygen
  • Breathe out into the tank and the upper half will rise
  • Breathe in from the tank and the upper half will fall
  • Trace marker is attached to the mobile upper half
25
Q

What is a peak flow meter?

A
  • Measures the rate at which air can be expelled from the lungs
  • The instrument produces a graph about the amount of the air they breathe out and how quickly they breathe out
26
Q

Why does the overall volume of gas in the spirometer tank decline over time?

A
  • The spirometer contains Soda Lime which absorbs CO2
  • When breathing, O2 is used up from the tank and CO2 is absorbed by the soda lime
  • Therefore, the gas volume of tank decreases over the experiment
27
Q

What is tidal volume?

A
  • Volume of air that moves into and out of the lungs with each resting breath
  • 0.5dm^3 is the adult average
  • Is 15% of the vital capacity
28
Q

What is vital capacity?

A
  • Largest volume of air that can be breathed in
  • When the strongest possible exhale is followed by the strongest possible inhale
  • 5dm^3 is the adult average
29
Q

What is inspiratory reserve volume?

A

-Maximum volume of air you can breathe in over and above normal inhalation

30
Q

What is expiratory reserve volume?

A

-Maximum volume of air you can force out of your lungs over and above the normal tidal volume of air you breathe out

31
Q

What is residual volume?

A

The volume of air that is left in your lungs when you have exhaled as much as possible

32
Q

Why must there always be some air in your lungs?

A

Because otherwise your lungs would completely collapse

33
Q

What is total lung capacity?

A
  • The sum of the vital capacity and the residual volume

- Total potential amount of air in the lungs at any one time

34
Q

What are the evolutionary strategies to gas exchange in fish?

A
  • Obligate air breathers need to breathe air or will suffocate (emerge at surface)
  • Facultative air breathers can breathe air if they need to but mainly rely on their gills
  • Fish that cannot breathe rely on gills for gas exchange
35
Q

How to gills work?

A

-Gas exchange takes place across the surface of gills

-

36
Q

What is the operculum?

A
  • Series of bones that act as facial support and protective gill covers
  • It adjusts the pressure of water in the pharynx to allow proper ventilation of the gills
  • Opercular Valves inside the mouth keep water from escaping
37
Q

What is the buccal cavity (pharynx)?

A
  • Bony fish inhale water through their mouth by lowering the floor of the buccal cavity and closing the opercular valves
  • They exhale water by raising the floor of the buccal cavity and closing the opercular valve to allow water out
  • This ensures water is always flowing over the gills
38
Q

What are gill arches?

A

A series of bony loops that support the gills

39
Q

What are gill filaments?

A

Occurs in large stacks and each stack is called a gill plate

40
Q

What are gill lamellae?

A
  • The main site of gas exchange

- They have a very large surface area

41
Q

What features to gills have to carry out efficient gas exchange?

A
  • Tips of adjacent gill filaments overlap to slow the flow of water down
  • Water moving across and through the gills and the blood flowing the gill filaments move in opposite directions
  • Large SA
  • A good blood supply
  • Thin walls
42
Q

What is the parallel system of gas exchange?

A
  1. Blood in gill filaments and the water moving across and through the gills both flow in the same direction
  2. Oxygen will diffuse down a steep concentration gradient at the leading edge of the gill filaments but equilibrium will be reached at some point before the wave leaves the gills
  3. This means the surface area of gill filaments is not being fully utilised for oxygen exchange between water and blood
  4. This is less efficient than the counter current flow
43
Q

What is the counter current flow system of gas exchange?

A
  1. The blood in the gill filaments and the water moving across and through the gills both flow in opposite directions
  2. Oxygen will diffusion down a reasonably steep concentration gradient along the whole length of the gill filaments, and then equilibrium is reached
  3. This means the entire surface area of the gill filaments is fully utilised for oxygen exchange between water and blood
  4. This is more efficient than a parallel flow system
44
Q

What are spiracles?

A

Holes in the thorax and abdomen walls, usually a pair for each segment and often with valves

45
Q

What are tracheae?

A

Tubes that lead into the body from the spiracles, which form a branching of ever smaller diameter tubes, strengthened by hoops or spirals of chitin called taenidia.

46
Q

What are tracheoles?

A
  • Single and greatly elongated cells that form minute tubes, found at the ends of the smallest tracheae
  • The site of gas exchange with body cells
47
Q

What is tracheal fluid?

A

Fluid in the tracheoles, but at the very end of each tracheole

48
Q

How do the spiracles work?

A
  1. Air enters and leaves the respiratory system of insects through the spiracles
  2. The spiracles can be opened and closed to reduce water loss (contracting muscles surrounding the spiracle, opening valve)
  3. Spiracles may also be surrounded by hairs to minimise water loss
  4. The spiracles open and close depending on the metabolic demands of the insects. So, when demand for oxygen is high, more spiracles will be open
49
Q

How does the insect tracheae work?

A
  1. After passing through a spiracle, air enters a complex branching network of tracheal tubes that subdivides into smaller diameters and reaches every part of the body
  2. To prevent its collapse under pressure, reinforcing wire of chitin winds spirally through the walls as hoops
  3. The gives the tracheal tubes the ability to flex and stretch without developing kinks that might restrict air flow
50
Q

How do the tracheoles and tracheal fluid work?

A
  1. Tracheoles penetrate into the spaces between body cells, so have a large surface area, so that gas exchange can meet metabolic demands
  2. They have no chitin and have very thin walls to create a short diffusion path
  3. The inside of the walls are moist with water, so gases can dissolve into the liquid phase
  4. Gas exchange happens at these surfaces, oxygen from the air dissolves in the moist lining of the tracheoles and diffuses into body cells
  5. Carbon dioxide follows the reverse path
51
Q

How do insects ventilate their respiratory system?

A
  1. Small insects rely entirely on passive diffusion of gases
  2. Whereas, large insects require active ventilation
  3. This is done by opening some spiracles and closing others while using abdominal muscles to alternatively expand and contract body movement
  4. This creates pulsating movements that flush air from one end of the body to the other through the tracheal system
52
Q

What may larger insects have?

A
  • Some larger insects will have air sacs as part of their tracheal system
  • These act as reservoirs of air and conserve water during periods of drought
53
Q

What is discontinuous gas exchange cycles?

A

-Occurs when insects are at rest and may help insects that are at rest in burrows or prevent the entry of pathogens through the spiracles
-Occurs in three phases:
Closed, Flutter and Open

54
Q

What is the closed phase of DGC?

A
  • Spiracles shut tight which drastically reduces ventilation with the external environment
  • O2 is consumed and its conc decreases within the tracheal system
  • CO2 is produced and increases in conc, it is buffered in the haemolymph rather than diffusing into tracheal system
  • This leads to a negative pressure and starts the flutter phase
55
Q

What is the flutter phase of DGC?

A
  • Spiracles open slightly and close in rapid succession
  • A small amount of air from the environment enters the respiratory system each time spiracles are opened
  • Fresh air is brought into the tracheal system to increase conc of O2, and releases small amounts of CO2
  • Most of the CO2 is still buffered by the haemolymph
56
Q

What is the open phase of DGC?

A
  • Flutter phase continues until until CO2 production surpasses the buffering capacity and begins to build up in the tracheal system
  • Spiracles open completely causing a rapid release of CO2. a complete exchange of gases with the environment occurs.
57
Q

What is the main difference in gas exchange between insects and mammals?

A
  • Insects have evolved a system to deliver oxygen and remove CO2 directly from each cell
  • This means the gas exchange system in insects is a separate system to their circulatory system, unlike in mammals

Biology (33 decks)

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